This invention relates to clamping devices of the worm drive type, and specifically, to a clamping device having a worm drive that is capable only of being tightened, and which cannot be loosened.
Worm drive clamps are used in a wide variety of industrial and other applications to tighten and loosen a band or strap in a circular direction. Such clamps may be used, for example, to provide a tight closure between two nesting tubes of similar, but slightly different, diameter, or to close a container having a flexible opening. A worm drive clamp typically comprises a worm drive member, or gear, having a spiral thread, a housing in which to situate the worm drive member, and a flexible strap that is fed through the housing and that has grooves or slots provided thereon that engage the spiral thread and cause the clamp to be tightened as the worm drive member is rotated.
Of particular interest to the present application is the use of worm drive clamps to close securely currency bags. These bags, typically made of a heavy cloth such as burlap, are used by banks and other financial institutions to transport hard currency, typically from one branch to another. Because these bags are filled by hand by bank or security personnel, it is important that the clamp be capable of being closed and sealed in an easy and efficient manner. Yet, given the application, it also is important that the clamp, once tightened, not be prone to being loosened while in transit.
There also exists a need in applications involving cloth or otherwise flexible containers for a clamp having a secondary hold on the container. Particularly with respect to thin plastic containers such as refuse bags, a clamp that appears to be fully tightened may later be effectively loosened as portions of the plastic gathered against each other by the clamp slip outside of the clamp.
In addition, since currency bags are re-used and different denominations of currency may be carried by the same bag at different times, it would be advantageous for the worm drive clamp to be able to indicate the contents of the bag. It also would be advantageous to keep to a minimum the number of separate parts required for the clamp.
Accordingly, it is an object of the present invention to provide a worm drive clamp suitable for closing the open end of a flexible container such that the clamp may be tightened, but may not be loosened.
It as another object of the present invention to provide a worm drive clamp having a strap and housing comprising a unitary member.
It is a further object of the present invention to provide a worm drive clamp having a strap that includes a tab portion to permit easy identification of the contents of the container sealed by the clamp.
It is a further object of the invention to provide a worm drive clamp having a strap that has penetrating members disposed on its inner surface such that as the clamp is tightened the penetrating members will pierce or otherwise lodge in the container material to hinder portions of the container material from accidentally slipping free from the clamp.
The foregoing objects are achieved in the present invention by a worm drive clamp comprising a worm drive member and a unitary strap and housing member. The worm drive member has a body with a spiral thread, a head above the body, a pawled portion below the body, and, preferably, a knob disposed below the pawled portion. The housing has a ratcheted recess adapted to engage the pawled portion of the worm drive member, as well as slot for receiving the end of the strap. The housing also has, preferably, a hole in its bottom wall to allow penetration by the knob of the worm drive member.
The end of the strap is inserted into the slot until grooves provided on its inner surface engage the thread on the body of the worm drive member. Then, as the head is rotated clockwise, the thread acts to pull the strap further through the slot, tightening the clamp. Meanwhile, the pawled portion of the worm drive member is engaged with the ratcheted recess of the housing so as to prevent rotation in the opposite direction. Thus, the clamp may be tightened but it may not be loosened.